Propeller stabilized and controlled torpedoes



T. G. LANG July 14, 1964 PROPELLER STABILIZED AND CONTROLLED TORPEDOESFiled NOV. 5, 1958 2 Sheets-Sheet 1 m MW m VG s A w m E m flm 0 T V. T BA mm 3 a 5 3 ll .11! Q9 F a m m. 8 Y 9 m mm mm a t mm 2 ll I F N N I 1 QN July 14, 1964 1'. e. LANG 3,140,635

PROPEZLLER STABILIZED AND CONTROLLED TORPEDOES Filed Nov. 5. 1958 2Sheets-Sheet 2 INVENTOR.

/ i9 5 THOMAS s. LANG 4! ATTofilYg.

United States Patent Ofifice 3,140,685 Patented July 14, 1964 tary ofthe Navy Filed Nov. 5, 1958, Ser. No. 772,146 4 Claims. (Cl. 114-43(Granted under Title 35, US. Code (1952), see. 266) The inventiondescribed herein may be manufactured and used by or for the Governmentof the United States of America for governmental purposes without thepayment of any royalties thereon or therefor.

This invention relates to underwater vehicles and more particularly toimprovements in propulsion, stabilizing and controlling apparatus fortorpedoes.

It is well known that torpedo hulls of conventional shape, generallydefined as circular in cross section with an ogival nose and taperedtail section, are inherently unstable in maintaining a desired coursedue to the lack of symmetry of the hydrodynamic forces acting on thehull. It has, accordingly, been conventional practice to provide suchtorpedoes with fixed fins at the tail, usually four in number, disposedin the vertical and horizontal planes. The hydrodynamic forces acting onsuch fins tend to stabilize, in pitch and yaw, the otherwise unstablehull and keep it on its desired course when it tends to deviate fromsame. It is also known that propellers. in addition to their propulsivefunction, tend to stabilize torpedoes similar to fins. The developmentof torpedoes of the type propelled by rotating propellers and stabilizedby fixed fins to operate at greater speeds has created severe problemsin attempting to produce torpedoes which operate quiet andcavitation-free. These are important factors to be considered with theadvent of the homing torpedo and increased speeds required of same forit to adequately intercept faster moving targets. A few of these andother problems may be briefly noted. For example, very smallmisalignments of fixed fins which may result from manufacturingtolerances or handling of a torpedo introduce large spurious moments onthe torpedo adversely affecting its performance. Shrouded propellershave been employed to suppress propeller cavitation but these areexpensive and introduce stability and control problems. The heavyloading on conventional propeller blades operating in the wake ofstabilizing fins is also conducive of cavitation. From thoseconsiderations it becomes apparent that the propeller-fixed fincombination is not necessarily the ideal arrangement for all torpedoesfor all purposes. The desirability of eliminating the stabilizing finsnormally employed on a torpedo hull ahead of the propeller has beenrecognized in a recent development as disclosed in the copendingapplication of Barnes W. McCormick et al., Serial No. 668,267, filedJune 26, 1957. In this development a single propeller is employed at therear end of a finless tail cone, behind which is disposed a multi-bladedfixed fin, the blades of which are suitably shaped to produce equal andopposite torque of the propeller to thus effect a zero torque on thetorpedo hull.

The present invention advances the development of the prior art,generally referred to, by a new concept, which, in its broadest aspects,provides a torpedo which is stabilized by contra-rotating propellerswithout the use of fixed stabilizing fins, this being the primary objectof the invention.

Another object is to both propel and stabilize a torpedo against pitchand yaw with contra-rotating propellers without the use of fixedstabilizing fins.

Another object, in a preferred embodiment of the invention, is topropel, stabilize and directionally control a torpedo withcontra-rotating propellers without the use of fixed stabilizing fins andmovable control surfaces, such as conventional rudders and elevators.

Another object is to reduce propeller cavitation by employing relativelylow speed, large diameter, lightly loaded, contra-rotating propellers.

Another object is to provide improvements in apparatus for opposing rollmoments of torpedoes having substantially torque balancedcontra-rotating propellers.

Another object is to provide a torpedo, the turning tendency of which isunaffected by damage to or misalignment of certain of its parts.

Further objects, advantages and salient features will become moreapparent from a consideration of the description to follow. the appendedclaims, and the accompanying drawing, in which FIGS. 1 to 3 areexemplary of the preferred embodiment of the invention above referredto, and wherein:

FIG. 1 is a longitudinal central section of the rearmost portion of thetail cone of a torpedo;

FIG. 2 is an enlarged section taken on line 22, FIG. 1;

FIG. 3 is a side elevation of a portion of the tail cone and a portionof the torpedo at its largest diameter showing, also, one form of rollcontrol; and

FIGS. 4A, 4B and 4C illustrate various forms of directional controlswhich may be employed in lieu of the preferred embodiment, abovereferred to.

Referring in detail to the drawing (FIG. 3), the torpedo 10 comprisesany conventional casing or hull having an intermediate section 11 and atail cone section 12, the former having the maximum diameter of thetorpedo. As shown in this figure propellers 13, 14 are the same diameteras the maximum diameter of the torpedo.

Referring now to FIG. 1, the tail cone is provided with a pair ofcoaxial shafts 15, 16, mounted for rotation in bearing 17 and rotated attheir forward ends by any suitable contra-rotating power supply,illustrated as the armature 18 and field 19 of an electric motor,connected to the shafts for rotating same in opposite directions anddistributing equal torque thereto. Motors of this type are well knownboth in general applications of power transmission and in the torpedoart hence specific details have been omitted in the interests ofclarity. Shaft 16 is connected to its rearward extension 16a by aconventional universal joint 20 while shaft 15 is connected to itsrearward extension 15:: by a conventional universal joint, this being inthe form of a splined sleeve 21, the splines of which engage curvedmating splines 22, 22a disposed on shafts 15, 15a, respectively. Aspherical type conventional anti-friction bearing 23, the inner andouter races of which may oscillate relatively about point 24 forms asupport for shaft 15a on shaft 15. The rear inside face of the tail coneis provided with a concave spherical surface 25, the radius of which isthe distance to point 24. A slideable swivel plate 26 having a matingconvex spherical face slideably engages surface 25 so that the axis ofshafts a, 16a may be oriented to various points on surfaces of coneshaving their apex at point 24. Shaft 15a, journaled in a bearing 27 andsupported by swivel plate 26 extends through the rear end of the tailcone and is secured in any desired manner to forward propeller 13. Shaft16a, journaled in shaft 15a and in bearing 28, extends to the rear ofpropeller 13 and is similarly secured to rear propeller l4. Suitableseals for preventing undesired fluid leakage into the torpedo hull orinto or out of the various parts of the mechanisms may be employed asdesired.

To effect angular orientation of shafts 15a, 16a relative to torpedoaxis 29 there is provided a roller bearing 30 contained in an orientableblock 31, the lateral movement of which is controlled by four hydraulicactuators 32 having pistons 33 the inner ends of which engage thebearing block in any suitable manner such as by abutments 34 having ballcontacts engaging block 31. The actuators may be hydraulically connectedto any conventional type hydraulic source which will move oppositepistons in opposite directions thereby disposing the axis of shafts 15a,16a at any desired angular position relative to axis 29. Since hydrauliccontrol actuators of this general type are employed for actuating theazimuthal (yaw) and elevational (pitch) rudders of torpedoes, furtherdetails are omitted in the interests of clarity. It is to be understood,however, that the actuators are under the control of the torpedoguidance system and function to guide the torpedo, by orientation of itspropellers, in a manner similar to conventional guidance by rudders.

While shafts 15, 1.6 will preferably be torque balanced with respect toeach other, bearing friction loss will apply a minor torque to thetorpedo hull tending to cause roll. This may be compensated for invarious ways. For example, the weight of the torpedo may be distributer'so that it is pendulous by choosing a center of gravity below axis 29.As illustrated in FIG. 3, an upper fin 45 and lower fin 46 are employedwith a torpedo having the weight so distributed, the area of the lowerfin being greater than that of the upper fin whereby the differen tialarea serves the purpose of opposing the pendulou: centrifugal forcesduring turns while the sum of the fin areas reduces transient rollduring turns. Shown in FIG. 1 is the preferable device for this purposecomprising a friction brake 40 which may be pivoted about pivot 41 toselectively engage brake shoes 42, 43 with the rotatable members 19, 18,respectively. Any suitable roll sensing device, such as a restrainedpendulum, may control actuator rod 44 to selectively engage one of theoppositely rotating brake shoes and thereby impart an opposing rolltorque to the hull in either of opposite directions.

Referring now to FIGS. 4A, 4B and 4C, these embodiments of the inventionare the same as that described for FIGS. 1 to 3 except that thepropellers rotate about a fixed axis, as in conventional torpedoes, andsmall movable rudders are provided for azimuthal, elevational and rollcontrol, these functioning in a manner similar to the conventionalrudders provided on prior art torpedoes.

FIG. 4A illustrates the tail cone of a torpedo provided with pairs ofrudders and FIGS. 4B and 4C illustrate two different locations ofsimilar rudders disposed on nose sections of torpedoes. In any of thesefigures, as compared with the preferred embodiment of the invention, therudders produce somewhat increased overall drag to the torpedo. Theembodiment of FIG. 4A also tends to produce propeller cavitation due toits wake effects resulting from large deflections and the close forwardproximity to the propellers. Nose rudders, as illustrated in FIG. 4Brequire larger deflection for turning, and may tend to eavitate. Thedrag of the torpedo is noticeably increased with the addition of anyfins. From the considerations, aforesaid, it becomes apparent that whereoptimum torpedo performance is desired the control means of thepreferred embodiment has certain advantages since it produces, inaddition to the advantageous effects previously mentioned, the quickestturn rate for the least deflection (of the propeller shafts), the leastdrag, and minimized cavitation.

The propellers employed may follow known design criteria but differ inthat they are of large diameter (approximately the maximum diameter ofthe torpedo). Their average cord length should be large as compared withthe smaller conventional highly loaded propellers This will result insome decrease in propeller efiiciency since they will have surface areaslarger than necessary for propulsion but they will be more eflicientthan the combination of the conventional smaller propellers and theassociated fixed fins required for stabilization. It can be shown thatthe conventional combination just referred to has approximately 15%greater drag than the hull of this invention used without thestabilizing fins. As to the average pitch of the blades, it will beapparent that if the pitch angle is 0, that is, the plane of the bladesis perpendicular to the axis of rotation, the blades produce nopropulsion, and also have no stabilizing effect. If this pitch angle isnow increased to the extreme of so that the blades now become flatpaddles in planes passing through the axis of rotation they againproduce no propulsive effect but produce maximum stabilization sincethey now act as fins disposed in the direction of torpedo movement, likefixed fins, differing in that they rotate. Since the blades obviouslymust produce both propulsion and stabilization their average pitch musttherefore be between these two extremes so that the optimum combinationof propulsive force (forward component of force on the blades) andstabilizing force (lateral stabilizing component of force on the blades)is chosen to produce the desired combination of these forces. This willvary for the particular application of the invention and the properdesign may be chosen by application of propeller design techniques knownin the art. Since the rear propeller operates in the wake of the frontpropeller and hence in a less favorable hydrodynamic stream than thefront propeller, it may be desirable, where cavitation must beminimized, to rotate the rear propeller at a lower speed than the frontpropeller. Cavitation may also be minimized in some instances byemploying propellers of unequal diameters. Similarly, the propellers maybe of unequal diameters and of unequal areas and rotatable at ditferentspeeds.

As referred to in the penultimate object, it is well known thatmisaligned or damaged stabilizing fins of conventional torpedoes producea tendency to turn. In the present invention, while the propellers servethe function of fixed stabilizing fins, a misaligned or damagedpropeller blade does not affect the turning because any tendency toproduce a side force at a particular point of rotation is balanced by anequal and opposite restoring force when the blade is disposed at a pointopposite to the particular point referred. As will be apparent, the sameeffect obtains regardless of the number of damaged or misalignedpropeller blades.

It can be shown that the requisite side or lateral controlling forcescreated by orienting the axis of the propellers away from the axis ofthe torpedo can be attained with small angles of orientation. In anexemplary torpedo having a finless hull, but otherwise comparable to aprior art hull with stabilizing fins, a 1 deflection produces an 18 persecond turn rate, adequate for most homing torpedoes.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A torpedo having an elongated hull devoid of fixed yaw and pitchstabilizing fins, tandem contra-rotating torque balanced propellersdisposed at its rear end, rotatable about its longitudinal axis, saidpropellers having a diameter at least substantially the maximum diameterof the hull and of suflicient area to solely effect stabilization of thetorpedo in yaw and pitch, means for rotating the propellers, and meansfor steering the torpedo to move it in desired directions.

2. A torpedo in accordance with claim 1 wherein said means for steeringcomprises means for selectively moving the axis of rotation of thepropellers angularly away from said longitudinal axis in any direction.

3. A torpedo in accordance with claim 1 including means for opposingroll moments which tend to roll the torpedo about said longitudinalaxis.

4. A torpedo in accordance with claim 3 wherein the means for opposingroll moments comprises means within the torpedo for applying torque tothe hull in either of opposite directions about its longitudinal axis bypower delivered from the means for rotating the propellers.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Marine Engineers Handbook, 1945, McGraw-Hill, New York,1408-1423.

1. A TORPEDO HAVING AN ELONGATED HULL DEVOID OF FIXED YAW AND PITCHSTABILIZING FINS, TANDEM CONTRA-ROTATING TORQUE BALANCED PROPELLERSDISPOSED AT ITS REAR END, ROTATABLE ABOUT ITS LONGITUDINAL AXIS, SAIDPROPELLERS HAVING A DIAMETER AT LEAST SUBSTANTIALLY THE MAXIMUM DIAMETEROF THE HULL AND OF SUFFICIENT AREA TO SOLELY EFFECT STABILIZATION OF THETORPEDO IN YAW AND PITCH, MEANS FOR ROTATING THE PROPELLERS, AND MEANSFOR STEERING THE TORPEDO TO MOVE IT IN DESIRED DIRECTIONS.